# GCObject documentation

rfm@gnu.org
Generated at 2025-02-13 06:02:40 +0000
2002 Free Software Foundation, Inc.
Software documentation for the GCArray class
GNUstepBase/GCObject.h
Description forthcoming.
Warning the underscore at the start of the name of this instance variable indicates that, even though it is not technically private, it is intended for internal use within the package, and you should not use the variable in other code.
Warning the underscore at the start of the name of this instance variable indicates that, even though it is not technically private, it is intended for internal use within the package, and you should not use the variable in other code.
Warning the underscore at the start of the name of this instance variable indicates that, even though it is not technically private, it is intended for internal use within the package, and you should not use the variable in other code.
Description forthcoming.
Software documentation for the GCDictionary class
GNUstepBase/GCObject.h
Description forthcoming.
Warning the underscore at the start of the name of this instance variable indicates that, even though it is not technically private, it is intended for internal use within the package, and you should not use the variable in other code.
Description forthcoming.
Software documentation for the GCMutableArray class
GNUstepBase/GCObject.h
Description forthcoming.
Warning the underscore at the start of the name of this instance variable indicates that, even though it is not technically private, it is intended for internal use within the package, and you should not use the variable in other code.
Warning the underscore at the start of the name of this instance variable indicates that, even though it is not technically private, it is intended for internal use within the package, and you should not use the variable in other code.
Warning the underscore at the start of the name of this instance variable indicates that, even though it is not technically private, it is intended for internal use within the package, and you should not use the variable in other code.
Warning the underscore at the start of the name of this instance variable indicates that, even though it is not technically private, it is intended for internal use within the package, and you should not use the variable in other code.
Description forthcoming.
Software documentation for the GCMutableDictionary class
GNUstepBase/GCObject.h
Description forthcoming.
Warning the underscore at the start of the name of this instance variable indicates that, even though it is not technically private, it is intended for internal use within the package, and you should not use the variable in other code.
Description forthcoming.
Software documentation for the GCObject class
GNUstepBase/GCObject.h

The GCObject class is both the base class for all garbage collected objects, and an infrastructure for handling garbage collection.

It maintains a list of all garbage collectable objects and provides a method to run a garbage collection pass on those objects.

Description forthcoming.
gcCollectGarbage

This method runs a garbage collection, causing unreferenced objects to be deallocated. This is done using a simple three pass algorithm -

Pass 1
All the garbage collectable objects are sent a -gcDecrementRefCountOfContainedObjects message.
Pass 2
All objects having a refCount greater than 0 are sent an -gcIncrementRefCountOfContainedObjects message.
Pass 3
All the objects that still have the refCount of 0 are part of cyclic graphs and none of the objects from this graph are held by some object outside graph. These objects receive the -dealloc message. In this method they should send the -dealloc message to any garbage collectable (GCObject and subclass) instances they contain.

During garbage collection, the +gcIsCollecting method returns `YES`.

gcIsCollecting
Returns a flag to indicate whether a garbage collection is in progress.
gcObjectWillBeDeallocated:
anObject
Called to remove anObject from the list of garbage collectable objects.
This method is provided so that classes which are not subclasses of GCObject (but which have the same initial instance variable layout) can use multiple inheritance (behaviors) to act as GCObject instances, but can have their own -dealloc methods.
These classes should call this in their own -dealloc methods.
gcDecrementRefCount
Decrements the garbage collection reference count for the receiver.
gcDecrementRefCountOfContainedObjects

Marks the receiver as not having been visited in the current garbage collection process (first pass of collection).

All container subclasses should override this method to call the super implementation then decrement the ref counts of their contents as well as sending the -gcDecrementRefCountOfContainedObjects message to each of them.

gcIncrementRefCount
Increments the garbage collection reference count for the receiver.
gcIncrementRefCountOfContainedObjects

Checks to see if the receiver has already been visited in the current garbage collection process, and either marks the receiver as visited (and returns `YES`) or returns `NO` to indicate that it had already been visited.

All container subclasses should override this method to call the super implementation then, if the method returns `YES`, increment the reference count of any contained objects and send the -gcIncrementRefCountOfContainedObjects to each of the contained objects too.

Software documentation for the GCObject(Extra) category
GNUstepBase/GCObject.h
This category implements accessor methods for the instance variables used for garbage collecting. If/when we can ensure that all garbage collecting classes use the same initial ivar layout, we can remove these methods and the garbage collector can access the ivars directly, making a pretty big performance improvement during collecting.
NB. These methods must *only* be used by the garbage collecting process or in methods called from the garbage collector. Anything else is not thread-safe.
gcAlreadyVisited
Description forthcoming.
gcNextObject
Description forthcoming.
gcPreviousObject
Description forthcoming.
gcSetNextObject:
anObject
Description forthcoming.
gcSetPreviousObject:
anObject
Description forthcoming.
gcSetVisited:
flag
Description forthcoming.